Food packaging

ABSTRACT

The present invention relates to a layered packaging film for fresh produce. The film provides a water vapour transmission rate of at least 30 g m−2 per day, and includes a polymer layer with a sealing temperature of 205° C. or less. The present invention also provides a comprising fresh produce enclosed by a packaging film, wherein the packaging film is sealed by an elongate seal extending along the underside of the package, and wherein the elongate seal has a sealing strength such that when the packaging film is lifted from the upper side of the fresh produce package the seal breaks permitting the packaging film to be removed from the fresh produce in a single lifting action.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of US filed on which is a NationalStage Application of International Patent Application No.PCT/GB2016/052887 filed Sep. 15, 2016, which claims priority from GreatBritain Patent Application No. 1516575.6, filed Sep. 18, 2015, thediscloses of each of which are incorporated herein by reference in theirentireties for any and all purposes.

FIELD OF THE INVENTION

The present invention relates to packaging for fresh produce, inparticular to a fresh produce package comprising fresh produce enclosedin a packaging film, to a process for packaging fresh produce, and tolayered packaging films suitable for packaging fresh produce. Thepresent invention is particularly applicable to the bulk packaging offresh produce.

BACKGROUND OF THE INVENTION

Low O₂ and elevated CO₂ concentrations reduce respiration rate, inhibitethylene (the plant hormone responsible for aging and ripeningprocesses) and inhibit microbial growth (if the CO2 concentration issufficiently high) of many fresh produce items. Accordingly, maintaininglow O₂ and elevated CO2 concentrations can increase the shelf life offresh produce. Control of O₂ and CO₂ levels is a key feature ofequilibrium modified atmosphere packaging for fresh produce. The optimumO₂ and CO₂ vary depending on the fresh produce in question.

Additionally, it is important to control the concentration of watervapour inside a fresh produce package, since a build-up of water vapourinside the package and in particular condensation on the surface offresh produce can increase the susceptibility to microbial decay. Somefresh produce items are particularly sensitive to excess moisture, andso it is important to provide packaging which can avoid such a build-up.Therefore, for many items of fresh produce, it is advantageous to usepackaging films which exhibit high water vapour transmission rates(WTVR), to facilitate diffusion of water vapour out of the packaging,thereby reducing the risk of microbial decay.

As described in U.S. Pat. No. 6,190,710, polyamide films such as nylon-6or nylon-66 provide a suitable WVTR for many fresh produce items. Inaddition, U.S. Pat. No. 6,190,710 describes how polyamide films used inpackaging can be perforated to provide control of O₂ and CO₂ diffusionbetween the atmosphere inside the package and the surroundingenvironment. Typically, polyamide films provide a significantly higherWVTR than polyolefin films.

However, a drawback of the polyamide films typically employed in highWVTR modified atmosphere packaging is that they are characterized byhigh melting points and a narrow sealing temperature range. This canmake the sealing of such films difficult and automated packagingprocesses, such as flow wrapping processes, challenging.

SUMMARY OF THE INVENTION

The present inventors have found that by providing layered packagingfilms, the above-mentioned problems can be overcome or reduced. Inparticular, the present inventors have produced a range of layeredpackaging films which provide the requisite high WVTR for many freshproduce applications, but which have improved sealing properties.Previously, a combination of suitable WVTR and low sealing temperaturefor this kind of application has been difficult to achieve.

Accordingly, in a first preferred aspect the present invention providesa layered packaging film suitable for packaging fresh produce,comprising a first layer of polymer film and a second layer of polymerfilm adhered to a first surface of the first layer of polymer film,wherein:

-   -   the first layer of polymer film comprises polyamide and has a        sealing temperature of 210° C. or more;    -   the second layer of polymer film is compositionally different        from the first layer of polymer film, has a thickness of 5 μm or        less, and has a sealing temperature of 205° C. or less; and    -   the layered packaging film has a water vapour transmission rate        of at least 30 g m⁻² per day.

The layered packaging film may further comprise a third layer of polymerfilm adhered to a second surface of the first layer of polymer film,wherein the third layer of polymer film is compositionally differentfrom the first layer of polymer film, has a thickness of 5 μm or less,and has a sealing temperature of 200° C. or less. The second layer ofpolymer film and the third layer of polymer film may be composed of thesame material. The third layer is particularly suitable for retailpackaging applications, for example in making bags containing gussets.In some embodiments it may be preferred that the third layer is notpresent.

The second layer of may be adhered directly to the first layer (i.e.with no intermediate later). The third layer may be adhered directly tothe first layer (i.e. with no intermediate later). The packaging filmmay consist essentially of the first, second and optionally third layersof polymer film.

Surprisingly, the present inventors have found that the adhesion of thesecond (and optionally third) layer of polymer film to the first layerof polymer film does not substantially decrease the WVTR of the firstlayer, and accordingly the present invention provides a combination ofthe desired low sealing temperature with the high WVTR required forpackaging some produce.

The films of the present invention are particularly useful in flowwrapping processes for continuous packaging of fresh produce.Accordingly, in a second preferred aspect the present invention providesuse of a layered packaging film according to the first aspect forpackaging fresh produce. For example, the layered packaging film may beused in a continuous (e.g. automated) process for packaging freshproduce, for example in a flow wrapping process.

One area where shelf-life extension by modified atmosphere packaging isparticularly important is in the supply chain from the originalgrower/packer through to the end retailer. Typically, the fresh producewill be packaged in bulk for some or all of the shipment fromgrower/packer to retailer. Therefore, modified atmosphere bulk packagingis an area of particular interest in the field. The ease of removal ofthe bulk packaging by the retailer or an intermediate packer is animportant consideration.

Conventionally, bulk modified atmosphere packaging of fresh produce hasinvolved putting batches of fresh produce into large bags made ofmodified atmosphere packaging films which are tied to seal them, asshown in FIG. 1.

The present inventors have found that using flow packaging processes forthe packaging of fresh produce in bulk can provide an elegant solution.In particular, the present inventors have found that using a flowpackaging process to package fresh produce enables a fresh producepackage to be formed having an elongate seal on its underside whichalthough hermetic has a seal strength low enough to permit the seal tobe easily broken for packaging removal. Accordingly, in a thirdpreferred aspect the present invention provides a fresh produce packagecomprising fresh produce enclosed by a packaging film, the fresh producepackage having an underside and an upper side, wherein the packagingfilm is sealed by an elongate seal extending along the underside of thepackage, and wherein the elongate seal has a sealing strength such thatwhen the packaging film is lifted from the upper side of the freshproduce package the seal breaks permitting the packaging film to beremoved from the fresh produce in a single lifting action. Typically,the fresh produce package is a modified atmosphere fresh producepackage.

As an alternative, an elongate tear line may be provided on theunderside of the package, wherein the tear line has a strength such thatwhen the packaging film is lifted from the upper side of the freshproduce package the tear line tears permitting the packaging film to beremoved from the fresh produce in a single lifting action. The tear linemay be provided by scoring (e.g. laser scoring) or by perforation (e.g.laser perforation) of the packaging film. In this alternative, thelocation and strength of any seal is not particularly limited.

Packaging fresh produce in this way reduces film usage and labour costs,and provides an attractive alternative to conventional bulk modifiedatmosphere packaging.

The films of the first aspect of the present invention are particularlysuitable as the packaging film used in the third aspect, since theirsealing properties are suited to providing an elongate seal with asuitable seal strength to permit removal of the film in a single liftingaction, and the water vapour transmission rate of the films is suitablefor packaging fresh produce which is sensitive to water. Where a filmaccording to the first aspect is used, the elongate seal or elongatetear line may alternatively be located on the upper surface of thepackage, or along one or more sides of the package (e.g. around aperimeter of the package). However, this is less preferred.

In a further preferred aspect the present invention provides a packagingprocess for fresh produce, comprising flow packing fresh produce to forma fresh produce package according to the third aspect of the invention.

In a further preferred aspect, the present invention provides a processfor the manufacture of a layered packaging film according to the firstaspect comprising extruding a first polymer for forming the first layerand a second polymer for forming the second layer and forming the firstand second polymers into a layered film. Typically, the first and secondpolymers are extruded simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a photograph of a typical bulk packaging arrangement usedconventionally.

FIGS. 2 to 6 illustrate a process for packaging fresh produce to providea fresh produce package according to an embodiment of the presentinvention.

FIG. 7 illustrates removal of packaging film from a fresh producepackage according to an embodiment of the present invention.

DETAILED DESCRIPTION

Preferred and/or optional features of the invention will now be set out.Any aspect of the invention may be combined with any other aspect of theinvention unless the context demands otherwise. Any of the preferredand/or optional features of any aspect may be combined, either singly orin combination, with any aspect of the invention unless the contextdemands otherwise.

Layered Packaging Film

The first layer of polymer film comprises polyamide. Typically, thefirst layer of polymer film has a water vapour transmission rate of atleast 30 g m⁻² per day, when measured separately from the second (andoptional third) layers of polymer film. It may have a water vapourtransmission rate of at least 50 g m⁻² per day, at least 70 g m⁻² perday, at least 100 g m⁻² per day, or at least 120 g m⁻² per day whenmeasured separately from the second (and optional third) layers ofpolymer film. The maximum water vapour transmission rate is notparticularly limited in the present invention but may be 200 g m⁻² perday or less, or 160 g m⁻² per day or less.

Water vapour transmission rate (WVTR) as used herein refers to the watervapour transmission rate determined according to ASTM E96, at 23° C. and50% relative humidity.

The water vapour transmission rate of a polymer film may be adjusted forexample by heat treating or orienting the film, as described in U.S.Pat. No. 6,190,710 which is hereby incorporated by reference in itsentirety and in particular for the purpose of describing and definingways of adjusting the water vapour transmission rate of a polymer film.

Typically, the first layer of polymer film has a thickness of at least 5μm, more preferably at least 10 μm, at least 15 μm or at least 18 μm.The first layer of polymer film may have a thickness of 30 μm or less,or 25 μm or less.

The first layer of polymer film may be composed of two or moresub-layers which taken together form the first layer of polymer film.The sub-layers may have identical composition to each other, or one ormore of the sub-layers may have a different composition. For example,one or more of the sub-layers may include an additive or additives asdescribed in more detail below. One or more of the sub-layers may besubstantially free from additives. Typically, all of the sub-layerscomprise the same polyamide.

Typically, the first layer of polymer film comprises PA6(polycaprolactam). It may comprise PA6 in combination with EVA(poly(ethylene vinyl acetate)), EBA (poly(ethylene butyl acrylate))and/or EMA (poly(ethyl methyl acrylate)). The first layer may compriseat least 1 wt % in total of EVA, EBA and/or EMA with respect to thetotal weight of the layered packaging film, e.g. at least 3 wt % or atleast 5 wt %. The first layer may comprise at least 85 wt% or less intotal of EVA, EBA and/or EMA with respect to the total weight of thelayered packaging film, e.g. 70 wt % or less, or 50 wt % or less. Theaddition of EVA, EBA and/or EMA permits the water vapour transmissionrate of the first layer of polymer film to be manipulated. Typically,the addition of these polymers tends to reduce the water vapourtransmission rate.

The first layer of polymer film has a sealing temperature of 210° C. ormore. For example, it may have a sealing temperature of 215° C. or more,or 220° C. or more. The maximum sealing temperature is not particularlylimited in the present invention, but is typically 300° C. or less, or250° C. or less. For example, PA6 has a sealing temperature of 220-245°C.

As used herein, the term sealing temperature is intended to be thelowest temperature at which the layer in question will melt sufficientlyto fuse with another layer of the same composition to form a hermeticseal when subjected to heat and pressure in a heat sealing apparatus.The sealing temperature may be measured using a Laboratory Heat Sealeraccording to ASTM F2029 at constant pressure and sealing time. Thepressure may be in the range from 0.05 MPa to 0.7 MPa (e.g. 0.5 MPa) andthe sealing time may be in the range from 0.15 s to 0.5 s (e.g. 0.3 s).The sealing temperature may be determined across a range oftemperatures, e.g. from 150° C. to 300° C. or 250° C.

Typically, the second layer of polymer film has a water vapourtransmission rate (when measured separately from the first layer ofpolymer film) which is less than the water vapour transmission rate ofthe first layer (when measured separately from the second layer). Forexample, the water vapour transmission rate of the second later may beat least 10 g m⁻² per day less than the water vapour transmission rateof the first layer, e.g. at least 20, at least 40 or at least 50 g m⁻²per day less.

The water vapour transmission rate of the second layer (when measuredseparately from the first layer of polymer film) is typically 100 g m⁻²per day or less, e.g. 80 g m⁻² per day or less, 60 g m⁻² per day orless, or 50 g m⁻² per day or less. It may be at least 10 g m⁻² per day,at least 20 g m⁻² per day, at least 30 g m⁻² per day or at least 50 gm⁻² per day.

Typically, the second layer of polymer film has a thickness of 5 μm orless, more preferably 4 μm or less, 3μm or less, or 2 μm or less.Typically, the second layer of polymer film has a thickness of at least0.53 μm or at least 0.8 μm.

The second layer of polymer film may be composed of two or moresub-layers which taken together form the second layer of polymer film.The sub-layers may have identical composition to each other, or one ormore of the sub-layers may have a different composition. For example,one or more of the sub-layers may include an additive or additives asdescribed in more detail below. One or more of the sub-layers may besubstantially free from additives. Typically, all of the sub-layerscomprise the same polymer. In some embodiments, it may be preferred thatthe second layer of polymer film is formed from a single layer (i.e.does not comprise sub-layers).

The second layer of polymer film has a sealing temperature of 205° C. orless. For example, it may have a sealing temperature of 200° C. or less,195° C. or less, 190° C. or less, 185° C. or less, 180° C. or less, 175°C. or less, 175° C. or less, or 165° C. or less. The minimum sealingtemperature is not particularly limited in the present invention, but istypically 100° C. or more, 125° C. or more, or 140° C. or more. Aparticularly suitable range is 165-195° C., or 135-200° C.

It is particularly advantageous if the second layer of polymer film hasa broad range of sealing temperatures, meaning that a hermetic seal maybe achieved at a range of different temperatures, since this makes itmore straightforward to use the films in different flow packingequipment and makes it simpler and quicker to achieve a hermetic seal,increasing the throughput of the machinery.

The second layer of polymer film may comprise:

-   -   (i) a copolyamide, such as PA6/66, PA6/12, optionally in        combination with a multipolyamide such as PA66/69/610/6I;    -   (ii) a blend of two or more polyamides (homo-, co- or        multi-polyamides, for example selected from the group consisting        of PA6 (polycaprolactam), PA66 (Polyhexamethylene adipamide),        PA12 (Polydodecanolactam), PA69 (Polyhexamethylene azelaamide),        PA610 (hexamethylene sebacamide), PA11        (Poly(l1-aminoundecanoamide), PA612 Poly(hexamethylene        dodecanoamide), PA6/66, PA6/12, and PA66/69/610/6I;    -   (iii) one or more styrene copolymers, optionally blended with PS        (polystyrene) or HIPS (high impact polystyrene), for example one        or more styrene copolymers selected from the group consisting of        SBS (styrene butadiene styrene copolymer), SBC (styrene        butadiene copolymers), SEBS (styrene ethylene butylene styrene),        SEPS (styrene ethylene propylene styrene), SIS (styrene isoprene        copolymers); or    -   (iv) a single homopolymer selected from PA11 and PA12.

As the skilled person will understand PA61 (included in multi-polyamidePA66/69/610/6I identified above) is polyhexamethylene isophthalamide.

Particularly suitable is a blend of PA6/66 with PA66/610/6I.Particularly suitable is SBS.

Where a copolyamide is combined with a multipolyamide, typically thesecond layer includes 40-90 wt % of copolyamide and 10-60wt % ofmultipolyamide.

The preferred and optional features of the second layer of polymer filmdescribed herein apply equally to the optional third layer of polymerfilm, if present.

The first, second and/or third layers may include one or more additives.

For example, anti-block additive may be added to reduce the risk ofblocking, which is the adhesion of two adjacent layers of film.Anti-block additive may be provided to the first, second and/or thirdlayers. Typically, it is provided to one or more sub-layers of the firstlayer of polymer film, in an amount of 0.1-5 wt % with respect to thetotal weight of that sub-layer. Alternatively, 0.1-5 wt % of anti-blockadditive may be added to the second and/or third layers of polymer film(or sub-layers thereof). The skilled person will be familiar with theselection of suitable anti-block additives. Suitable anti-blockadditives include Ultramid B4OLN available from BASF (a high viscosityPA6 with enhanced formability due to the addition of nucleating and slipagents), and Styrolux NB10 available from Styrolution (an SBC polymerincluding an active wax system to reduce sheet blocking).

An anti-fog additive may be added to reduce fogging of the layeredpackaging film. The anti-fog additive may be added to any one of thelayers or sub-layers, e.g. at a level of 0.1-20 wt % with respect to thetotal weight of the layer or sub-layer to which it is added, e.g. at alevel of 0.5-15 wt %. The skilled person will be familiar with theselection of suitable anti-fog additives. Suitable anti-fog additivesinclude Polybatch AF1088 (a polyolefin based anti-fog additive)available from A. Shulman.

A bonding agent may be added to the second and/or third layers ofpolymer film to enhance bonding. The skilled person is familiar with theselection of suitable bonding agents. Typically, the bonding agent isadded where the second and/or third layer comprises one or more styrenecopolymers. Bonding agent is typically added at a level of 5-40 wt %,e.g. 10-35 wt % with respect to the total weight of the layer orsub-layer to which it is added.

Suitable bonding agents are modified polyolefins, e.g. a modified linearlow density polyethylene. The polyolefin may be modified with maleicanhydride. A suitable bonding agent is Orevac 18910 available fromArkema.

The particular layers that are chosen for any particular fresh producepackaging application is determined by factors such as produce to bepacked, supply chain length, sensitivity to excess moisture, sensitivityto dehydration and surface area to volume ratio. For example, Galiamelons are sensitive to excess moisture that aggravates superficialmould. On the other hand, the thick peel of the melons means that theyare not particularly sensitive to dehydration. As such, a film with awater vapour transmission rate of 145 g m⁻² per day is suitable forshipment of Galia melons from Brazil to mainland Europe.

Typically, the layered packaging film of the present invention has atotal thickness of 50 μm or less, e.g. 40 μm or less or 25 μm or less.It may have a thickness of at least 5 μm, or at least 10 μm.

Typically, the layered packaging film of the present invention has awater vapour transmission rate of at least 30 g m⁻² per day. It may havea water vapour transmission rate of at least 50 g m⁻² per day, at least70 g m⁻² per day, at least 100 g m⁻² per day, or at least 120 g m⁻² perday. The maximum water vapour transmission rate is not particularlylimited in the present invention but may be 200 g m⁻² per day or less,or 160 g m⁻² per day or less. The layered packaging film preferably hasa suitable water vapour transmission rate to provide little or nocondensation on the internal surface of the packaging film when used topackage fresh produce under typical storage and shipment conditions ofthe produce in question.

Typically, the layered packaging film of the present invention isperforated to provide suitable O₂ and CO₂ permeability for the freshproduce which is to be packaged, as described in U.S. Pat. No. 6,190,710which is hereby incorporated by reference in its entirety and inparticular for the purpose of describing the perforation of packagingfilms to increase O₂ and CO₂ permeability. The number, size and patternof the perforations required depend on the respiration rate of theproduce to be packed and the desired modified atmosphere

For example, the layered packaging film may be macroperforated toprovide holes having a diameter of approximately 1-10 mm covering up toabout 0.5% of the surface area of the packaging film, and/or thepackaging film may be microperforated to provide holes having a diameterof about 0.05-1 mm diameter at a density of up to about 2000 holes persquare metre of material. Preferably, the packaging film ismicroperforated to provide holes having a diameter of about 0.1-0.8 mmdiameter at a density of up to about 500 holes per square metre ofmaterial. Microperforations are typically provided by laser.Macroperforations may be provided by physical puncturing or cutting ofthe film.

For example, a packaging film used for packing 5 kg of Galia melons in a40×30 cm carton typically contains a total of 44 laser perforations of125±15 μm, and will provide modified atmosphere conditions of 10-15% O₂and 5-10% CO₂ under steady state conditions at 7° C., the optimalstorage temperature for Galia melons. The packaging films of the presentinvention may advantageously be used for bulk packaging of melons, suchas Galia melons.

Typically, the layered packaging film of the present invention is formedby extruding a first polymer for forming the first layer and a secondpolymer for forming the second layer and forming the first and secondpolymers into a layered film. Typically, the first and second polymersare extruded simultaneously (co-extruded). The extrusion is typicallythrough annular film dies, e.g. with manifolds for the different layersbeing located at different radial distances from the centre of the die.Air is typically injected into the centre of the die to inflate a bubbleof extruded polymer. The bubble is typically then cooled and collapsedto form a flat film. The layered packaging film is typically rolled toprovide a roll of packaging film once cooled. The skilled person will befamiliar with techniques for forming layered polymer films by extrusion.

Fresh Produce Package

The present invention provides a fresh produce package comprising freshproduce enclosed by a packaging film. Preferably, the fresh produce isenclosed by a single piece of packaging film.

The fresh produce is typically held in a container inside the packagingfilm. The material of the container is not particularly limited, but maybe for example cardboard, wood, pulp or plastic. Typically, thecontainer is open at the upper side to allow the fresh produce to beviewed from the top. This also allows the modified atmosphere packagingto function most effectively. Accordingly, the container may be a tray,for example.

An elongate seal extends along the underside of the package. Preferablythe elongate seal extends substantially entirely from one side of theunderside of the package to the other side of the package, to facilitateremoval of the packaging film as described herein. Preferably theelongate seal extends substantially along a middle line of the undersideof the fresh produce package.

Typically, the packaging film is in the form of a tube (formed bysealing a single piece of packaging film with the elongate seal), whichtube is sealed at both ends to enclose the fresh produce. The end sealsare typically hermetic.

The elongate seal may preferably be a fin seal. Alternatively, it may beformed by overlapping edges of packaging film to form an overlap seal.

The skilled person will understand that the underside of the package isthe part of the package which is typically positioned below the freshproduce during packing, storage, transport and/or display. The upperside is on the opposite side of the package, and typically positionedabove the fresh produce during packing, storage, transport and/ordisplay. Where the fresh produce is held in a tray or other container,the underside of the package is typically directly beneath the base ofthe tray or container.

The packaging film can be removed by lifting from the upper side of thefresh produce package in a single lifting action. During packagingremoval, typically the elongate seal breaks along at least 60% or atleast 80% of its length. For example, it may break along substantiallyits entire length. Typically, the seal Is broken by the weight of thefresh produce acting against the seal as the packaging film is liftedfrom the upper side of the fresh produce package in an upward direction.

The seal typically has a seal strength of at least 4 MPa. This providesadequate seal strength to ensure that the package remains sealed duringtransit. The seal typically has a seal strength of less than 20 MPa,less than 15 MPa or less than 10 MPa. This means that the packaging filmcan easily be removed in a single lifting action as described herein.

Seal strength is measured according to ASTM F88. A 15 mm width sample offilm containing the seal is cut out from the bag. Each tail of thesealed specimen is secured in the opposing grips of a Lloyd LRX tensiletester. The maximum tensile force required to separate the two ends ofthe seal is recorded.

The elongate seal is typically formed by applying heat and pressure toclamp two areas of packaging film together and cause them to fuse (e.g.two edges of a single piece of packaging film). The fused area forms theelongate seal. Typically, the elongate seal is a hermetic seal.Typically, the elongate seal has a width of between about 2 mm and about20 mm.

The fresh produce package comprises fresh produce enclosed by apackaging film. The packaging film may advantageously be a layeredpackaging film as described and defined herein. However, this is notessential.

Other suitable films include single layer packaging films, such assingle layer packaging films comprising PA6 blended with one or moreco-polyamides or multi-polyamides, or a single layer packaging filmcomprising co-polyamides optionally blended with a multi-polyamide. Thesingle layer films may include one or more additives as described anddefined above with reference to the layered packaging film. Theco-polyamide and multi-polyamides are typically as described and definedabove with reference to the layered packaging film.

The single layer packaging film may be composed of two or moresub-layers which taken together form the packaging film. The sub-layersmay have identical composition to each other, or one or more of thesub-layers may have a different composition. For example, one or more ofthe sub-layers may include an additive or additives. One or more of thesub-layers may be substantially free from additives. Typically, all ofthe sub-layers comprise the same polymer or polymer blend. In someembodiments, it may be preferred that the single layer packaging filmdoes not comprise sub-layers.

Typically, the packaging film useful in the fresh produce package of thepresent invention has a water vapour transmission rate as describedabove with reference to the layered packaging film. Typically, thepackaging film useful in the fresh produce package of the presentinvention is perforated to provide suitable O₂ and CO₂ permeability forthe fresh produce in question, as described above with reference to thelayered packaging film.

The fresh produce package is typically a modified atmosphere package. Asused herein, modified atmosphere packaging is intended to includepackaging wherein the packaging film has been selected or modified tocontrol one or more of the water vapour, CO₂ and O₂ concentrationsinside the package in order to prolong the shelf life of the packagedfresh produce.

As used herein, the term fresh produce is intended to include fruits,vegetables, flowers, plants, fungi and other edible or inediblehorticultural or botanical products which are perishable and tend tospoil or otherwise have a limited shelf life. The present invention isparticularly suitable for packaging fruits and vegetables that benefitfrom modified atmosphere packaging and that are suitable for packing ina container that is subsequently flow packed such as Galia andcantaloupe melons, pomegranates, stone fruits, including nectarines,peaches and plums and kiwi.

The fresh produce package of the present invention is particularlysuitable for packaging bulk produce, e.g. for all or part of the supplychain from the original producer through to the end retailer. Typically,bulk packaging contains between 2 kg to 20 kg of fresh produce, e.g. atleast 2 kg, at least 3 kg, at least 5 kg or at least 10 kg.

Where an elongate tear line is provided along the underside of thepackage, preferably the elongate tear line extends substantiallyentirely from one side of the underside of the package to the other sideof the package, to facilitate removal of the packaging film as describedherein. Preferably the elongate tear line extends substantially along amiddle line of the underside of the fresh produce package.

The packaging film can be removed by lifting from the upper side of thefresh produce package in a single lifting action. During packagingremoval, typically the elongate tear line breaks along at least 60% orat least 80% of its length. For example, it may break alongsubstantially its entire length.

An example packaging process according to an embodiment of the presentinvention will now be described with reference to FIGS. 2 to 6, andremoval of the packaging film will be described with reference to FIG.7.

FIG. 2 shows a tray 1 containing fresh produce 3 (e.g. melons) on aconveyor 5. The conveyor 5 moves the tray 1 into a horizontal flowpackaging machine. Packaging film 7 (see FIG. 3) is supplied to the flowpack machine and formed into an elongate tube enveloping the tray 1. Asshown in FIG. 3, a longitudinal fin seal 9 is formed along the underside8 of the tray 1 by applying heat and pressure to form the seal 9. Thelongitudinal fin seal 9 is hermetic but is sufficiently weak that thefilm may readily be removed from the tray of fresh produce in a singlelifting action as described below with reference to FIG. 7.

The film 7 is typically perforated prior to its supply to the flow packmachine to provide the desired O₂ and CO₂ transmission rates for thefresh produce 3 as described herein. The film 7 is supplied in asuitable orientation that the laser perforations are located on theupper side 10 of the package.

Where a layered packaging film according to the first aspect of theinvention is used as the film 7, the film 7 is supplied in a suitableorientation that the second layer is on the underside of the film 7 sothat two areas of the second layer come into contact with each other forforming the longitudinal fin seal 9.

As shown in FIG. 4, two cross seals 11,13 are formed by applying heatand pressure to seal the package 15. The package 15 is cut from theupstream package 17 and the downstream package 19.

As shown in FIG. 5, the package 15 is then transferred by conveyor 5 toa boxing area where the package 15 is placed in a crate 21 as shown inFIG. 6. Alternatively, the crate 21 may be provided on a lower conveyerand the package 15 slides into the carton from above.

When the crate 21 reaches its final destination, which may be asupermarket, the packaging film 7 is easily removed as shown in FIG. 7.The film 7 is lifted from the top, which supplies sufficient force tothe fin seal 9 on the underside of the package to allow the film 7 to beremoved from the tray 1 of fresh produce 3 in a single lifting action.The fresh produce 3 can be displayed by a retailer in the tray 1 withoutthe need to transfer the fresh produce 3 to another container.

EXAMPLES

Layered packaging films according to the present invention were preparedby extrusion through blown film dies. Extruders were used to melt andpush molten resin into an annular film die. Each layer was formed by aseparate spiral mandrel manifold at a different radial distance from thecentre of the die. Air was injected into the centre of the annular dieto inflate the polymer bubble. The bubble was cooled by an air ring thatblows air on the surface of the bubble to lower its temperature until itsolidifies. Above the die, a stabilizing cage was used to minimizemovement of the bubble as it was collapsed in the collapsing frame tomake a flat film. This film was then pulled over rolls and fed into afilm winder to make the finished film roll.

The following temperature profile was used to prepare the layered films:

Barrel Screen zones,

 C. Changer, Adaptor, Die, 1 2 3 4

 C.

 C.

 C. A—Seal Layer 200 210 230 240 240 245 245 B 230 245 245 250 250 250250 C 230 245 245 250 250 250 250 D 230 245 245 250 250 250 250 E 230245 245 250 250 250 250

Testing Methods Thickness was measured at 24 points across the width ofthe film using a Millimess Inductive

Digital Comparator Extramess 2001

WVTR was measured at 23° C. and 50% relative humidity according to ASTME96

Seal strength was measured according to ASTM F88. A 15 mm width sampleof film containing the seal is cut out from the bag. Each tail of thesealed specimen is secured in the opposing grips of a Lloyd LRX tensiletested. The maximum tensile force required to separate the two ends ofthe seal was recorded.

Sealing temperature range was measured using a Laboratory Heat Sealeraccording to ASTM F2029 at constant pressure and time. Dwell time was0.15-0.5 s in a temperature range of 150-200° C.

Materials

The following materials were used in the Examples below:

Copolymer 1 PA6/66 - available from BASF under brand name Ultramid C33LN Copolymer 2 PA66/69/610/6I - available from EMS-GRIVORY under brandname Grilon BM16 PA6 Available from DSM under brand name Akulon(polycaprolactam) F136-E1 Anti-Block Additive 1 Available from BASFunder brand name Ultramide B40LN Anti-Block Additive 2 Available fromStyrolution under brand name Styrolux NB10 Anti-Fog Additive Availablefrom Shulman under brand name Polybatch AF1088 SBC Available fromStyrolution under brand name Styrolux 684D Bonding Agent Available fromArkema under brand name Orevac 18910

Abbreviations:

PA6 Polycaprolactam PA66 Polyhexamethylene adipamide PA69Polyhexamethylene azelaamide PA610 Polyhexamethylene sebacamide PA6IIsophthalic acid SBC Styrene butadiene copolymer

Example 1—Films with Blended Polyamide Sealing Layer

Four examples of film structures having a sealing layer formed from ablend of copolyamides were prepared by the process described above, andtested for WVTR, sealing temperature and sealing strength using thetesting methods described above. The compositions and testing resultsare given below.

Example 1.1

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer Copolymer 1 78 Copolymer 2 20 Anti-Block Additive 1 2 2 3.7 HighWVTR PA6 100 3 8 Layer PA6 100 4 3.7 PA6 100 5 3.6 PA6 100

Example 1.2

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer Copolymer 1 48 Copolymer 2 50 Anti-Block Additive 1 2 2 3.7 HighWVTR PA6 100 3 8 Layer PA6 100 4 3.7 PA6 100 5 3.6 PA6 100

Example 1.3

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer Copolymer 1 70 Copolymer 2 20 Anti-Block Additive 1 2 Anti-FogAdditive 8 2 3.7 High WVTR PA6 100 3 8 Layer PA6 100 4 3.7 PA6 100 5 3.6PA6 100

Example 1.4

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer Copolymer 1 70 Copolymer 2 20 Anti-Block Additive 1 2 Anti-FogAdditive 8 2 3.7 High WVTR PA6 92 Layer Anti-Fog Additive 8 3 8 PA6 1004 3.7 PA6 100 5 3.6 PA6 100

Example 2—Films with Styrene-Based Sealing Layer

Two examples of film structures having a sealing layer formed from ablend of styrene copolymer and a bonding agent were prepared by theprocess described above. The compositions of the films are given below.

Example 2.1

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer SBC 74 Bonding Agent 25 Anti-Block Additive 2 1 2 3.7 High WVTRPA6 100 3 8 Layer PA6 100 4 3.7 PA6 100 5 3.6 PA6 100

Example 2.2

Layer Thickness/μ Functionality Composition Dosage/wt % 1 1 SealingLayer SBC 69 Bonding Agent 30 Anti-Block Additive 2 1 2 3.7 High WVTRPA6 100 3 8 Layer PA6 100 4 3.7 PA6 100 5 3.6 PA6 100

Testing Results

Packaging films prepared according to Examples 1 and 2 above were testedas described above. The results were as follows:

Sealing WVTR/g m⁻² Temperature/ Sealing Example Thickness/μm day⁻² ° C.Strength/MPa 1.1 19.8 ± 3 145 165-195 >4 1.2 19.7 ± 4 145 165-195 >4 1.320.1 ± 4 145 165-195 >4 1.4 20.1 ± 4 145 165-195 >4 2.1 20.7 ± 5 145165-195 >4 2.2 20.7 ± 5 145 165-195 >4

The WVTR of a 20 μm film of PA6 is also 145 g m⁻² day⁻², and accordinglyit can be seen that the addition of the sealing layer does not adverselyaffect the WVTR. However, the sealing temperature of PA6 is 220-245° C.,and accordingly it can be seen that the addition of the sealing layeradvantageously reduces the sealing temperature.

1. A layered packaging film suitable for packaging fresh produce,comprising a first layer of polymer film and a second layer of polymerfilm adhered to a first surface of the first layer of polymer film,wherein: the first layer of polymer film comprises polyamide and has asealing temperature of 210° C. to 300° C.; the second layer of polymerfilm is compositionally different from the first layer of polymer film,has a thickness of 0.5 μm to 5 μm, and has a sealing temperature of 100°C. to 205° C.; and the layered packaging film has a water vapourtransmission rate of at least 30 g m⁻² per day; and the layeredpackaging film is arranged such that the second layer of polymer film isthe outermost surface of the layered packaging and is configured as asealing layer for forming seal of a package, wherein the second layer ofpolymer film comprises: (i) a copolyamide, such as PA6/66, PA6/12,optionally in combination with a multipolyamide such as PA66/69/610/6I;(ii) a blend of two or more polyamides (homo-, co- or multi-polyamides,for example selected from the group consisting of PA6 (polycaprolactam),PA66 (Polyhexamethylene adipamide), PA12 (Polydodecanolactam), PA69(Polyhexamethylene azelaamide), PA610 (hexamethylene sebacamide), PA11(Poly(l1-aminoundecanoamide), PA612 Poly(hexamethylene dodecanoamide),PA6/66, PA6/12, and PA66/69/610/6I; (iii) one or more styrenecopolymers, optionally blended with PS (polystyrene) or HIPS (highimpact polystyrene), for example one or more styrene copolymers selectedfrom the group consisting of SBS (styrene butadiene styrene copolymer),SBC (styrene butadiene copolymers), SEBS (styrene ethylene butylenestyrene), SEPS (styrene ethylene propylene styrene), SIS (styreneisoprene copolymers); or (iv) a single homopolymer selected from PA11and PA12.
 2. A layered packaging film according to claim 1 having awater vapour transmission rate of at least 50 g m⁻² per day.
 3. Alayered packaging film according to claim 1, wherein the first layer ofpolymer film comprises two or more sub-layers.
 4. A layered packagingfilm according to claim 1, wherein the second layer of polymer film hasa sealing temperature of 100° C. to 200° C.
 5. A layered packaging filmaccording to claim 1, wherein the second layer of polymer film comprisesa blend of PA6/66 with PA66/69/610/6I.
 6. A layered packaging filmaccording to claim 1, wherein the second layer of polymer film comprisesSBS.
 7. A fresh produce package comprising fresh produce enclosed by thepackaging film of claim 1, the fresh produce package having an undersideand an upper side, wherein the packaging film is sealed by an elongateseal extending along the underside of the package, and wherein theelongate seal has a sealing strength such that when the packaging filmis lifted from the upper side of the fresh produce package the sealbreaks permitting the packaging film to be removed from the freshproduce in a single lifting action.
 8. A fresh produce package accordingto claim 7, which is a bulk fresh produce package.
 9. A fresh producepackage according to claim 8, comprising at least 2 kg of fresh produce.10. A fresh produce package according to claim 7, wherein the freshproduce is held in a container inside the packaging film.
 11. A freshproduce package according to claim 7, wherein the fresh produce isenclosed in a single piece of packaging film.
 12. A fresh producepackage according to claim 7, wherein the elongate seal extendssubstantially entirely from one side of the underside of the package tothe other side of the underside of the package.
 13. A fresh producepackage according to claim 7, wherein the elongate seal extendssubstantially along a middle line of the underside of the package.
 14. Afresh produce package according to claim 7, wherein the elongate seal isa fin seal.
 15. A fresh produce package according to claim 7, whereinthe elongate seal has a seal strength in the range from 2 MPa to 20 MPa.16. A packaging process for fresh produce, comprising flow packing freshproduce to form a fresh produce package as defined in claim
 7. 17. Aprocess for the manufacture of a layered packaging film as defined inclaim 1 comprising extruding a first polymer for forming the first layerand a second polymer for forming the second layer and forming the firstand second polymers into a layered film.
 18. The layered packaging filmaccording to claim 1, wherein the first layer of polymer film furthercomprises one or more of EVA, EVB and EMA.
 19. The layered packagingfilm according to claim 1, wherein the layered packaging film (1)consists essentially of the first layer of polymer film and the secondlayer of polymer film; or (2) consists essentially of the first layer ofpolymer film, the second layer of polymer film, and a third layer ofpolymer film.